GENETIC-ANALYSIS OF A PHOTOPERIOD RESPONSE GENE ON THE SHORT ARM OF CHROMOSOME 2(2H) OF HORDEUM-VULGARE (BARLEY)

RFLP mapping of 94 doubled haploid lines from a winter x spring barley cross (Igri x Triumph) identified a previously undescribed major phot operiod response locus (Ppd-H1) on the short arm of barley chromosome 2(2H). Lines with the Igri allele (winter parent) flowered 10 days ear lier under long days in a glasshouse experiment. The Ppd-H1 locus also had a major effect in field experiments, giving differences of 12 day s (spring sowing) and 7 days (autumn sowing). The Ppd-H1 locus account ed for 60 per cent of the genetic variation in flowering time in the s pring sowing and 46 per cent in the autumn sowing. The most likely loc ation of Ppd-H1 was in the 6 cM interval between the RFLP loci XMWG858 and XpsrB9, 1 cM proximal to XMWG858. The map position of Ppd-H1 sugg ests that it may be a homoeoallele of the wheat photoperiod response g ene Ppd1. Field data also showed that the barley Ppd-H1 locus was asso ciated with highly significant effects on plant height, biomass and yi eld components which were probably the direct results of the variation in flowering time. Flowering time and other agronomic characters were also significantly affected by an additional developmental!rate gene on the same chromosome.